Natural water (HO), the purest that can be obtained, cleared if necessary by filtration; free from odour, taste, and visible impurity. If pure it leaves no residue when evaporated, but it is very difficult to ensure absolute purity, on account of traces of foreign matter that are liable to be introduced from the still.
Prep. Made by distilling water in a still, rejecting the first portion.
Prop. & Comp. A limpid colourless fluid, devoid of taste and smell, not altered by the addition of lime-water, chloride of barium, nitrate of silver, oxalate of ammonia, or sulphuretted hydrogen, indicating freedom from carbonic acid or carbonates, sulphates, chlorides, and most organic matter, lime and ordinary metallic impurities, as copper, lead, etc. Composition (HO).
Use. It is ordered to be used in making almost all pharmaceutical preparations, but common water is frequently substituted; in some cases this neglect is important, as insoluble and inert compounds are formed, and the solvent power of distilled water for some substances exceeds that of common water.